Hydraulic binder

ABSTRACT

PRODUCTION OF A CEMENT-BASED HYDRAULIC BINDER CONTAINING FROM 10 TO 80% BY WEIGHT, PREFERABLY FROM 15 TO 70% BY WEIGHT SLAG GROUND TO CEMENT FINENESS AND ORIGINATING FROM THE ELECTROTHERMAL PRODUCTION OF PHOSPHORUS, AND USE OF THE HYDRAULIC BINDER FOR MAKING MASSIVE CONCRETE.

United States Patent 0 Int. c1. co4b7/02, 7/14 US. Cl. 106-89 ABSTRACT OF THE DISCLOSURE Production of a cement-based hydraulic binder containing from 10 to 80% by weight, preferably from to 70% by weight ground to cement fineness and originating from the e ectrothermal production of phosphorus, and use of the hydraulic binder for making massive con crete.

2 Claims This application is a continuation of applicants parent application U.S. Ser. No. 711,875, filed Mar. 11, 1968, copending herewith and now abandoned.

The present invention relates to a cement-based hydraulic binder.

The binders used in concrete generally comprise Portland cement or blast-furnace Cement. The starting materials used for making Portland cement comprise natural minerals, such as limestone, clay, clay marl or lime marl, and calcium sulfate, which are intimately mixed and then calcined, for example in a rotary kiln. After grinding to the desired fineness, there is obtained a so-called hydraulic binder which hardens in contact with water. Blast-furnace cement is produced from material, wherein the natural minerals are partially replaced by quenched blast-furnace slag which also ha latent hydraulic properties.

A property characteristic of conventional standard cements is their ability to harden relatively rapidly, the hardening being substantially complete after 28 days. Blast-furnace cement has more particularly been found to be subject to a certain degree of after-hardening which, however, is of substantially no interest for practical purposes.

To be suitable for making massive concrete, i.e. for the production of large-dimensioned concrete bodies, it is an important requirement for the setting cement to have no more than a fair heat-evolution rate per unit of time. Failing this, the concrete mass would be subject to internal stress and possible cracking. As a result of its lower hardening velocity, blast-furnace cement has a heat evolution rate per unit of time slightly lower than that of Portland cement which, however, is still high enough to produce deleterious effects.

Attempts have already been made separately to grind blast-furnace slag to cement fineness and to add the ground slag to Portland cement on the construction site, but this entails disadvantages, these being the same as those reported above.

Natural puzzuolanes, for example trass, whose special properties make it an additive very suitable for use in water-proof concrete, have been found to behave in a similar manner.

The electrothermal production of phosphorus from phosphates is known to entail the formation of slag, which is called hereinafter phosphorus furnace slag and has a chemical composition difierent from that of Portland cement or blast-furnace slag, with respect to its individual constituents.

Phosphorus furnace slag has long been held to be unsuitable for the production of hydraulic binders, particularly in view of the very slight proportions of aluminum oxide contained therein. Typical of phosphorus furnace slag is, for example, the following composition:

Cement, more particularly Portland cement, containing from 10 to by weight, preferably from 15 to 70% by weight, of slag, ground to cement fineness and originating from the electrothermal production of phosphorus, has now unexpectedly been found to be a hydraulic binder very suitable for use in massive concrete. In concrete produced with the hydraulic binder of the present invention, the increase in strength occurs more slowly than in concrete made with pure Portland cement or blastfurnace cement, but this is accompanied by an extremely long after-hardening period for the concrete, which is unexpectedly substantially longer than that of concrete produced with standard cements and incomplete even after 360 days.

It has been found that concrete made with the binder of the present invention has a strength greater than that of concrete produced with pure Portland cement, after 360 days. However, the most important property of the hydraulic binder of the present invention resides in the fact that concrete produced therewith has a heat-evolution rate considerably lower, particularly during the first days, than that of concrete produced with standard cements. In other words, the concrete mixtures so made are of considerable interest for the production of concrete bodies having large dimensions.

The phosphorus furnace slag can be mixed with the Portland cement either by grinding the two binder components separately and then mixing them, or by grinding the phosphorus furnace slag together with the Portland cement clinker. No difference in the strength of the concrete has been observed.

It has already been proposed to use foamed phosphorus furnace slag as an additive in the production of building materials, particularly lightweight concrete. However, this is granular phosphorus furnace slag which has no hydraulic properties. With this in mind, it is all the more an unexpected result that ground phosphorus furnace slag does possess such hydraulic properties.

EXAMPLE 1 Phosphorus furnace slag having the following composition:

was ground so as to have a Blaine-index of 3470 sq. cm./gram and then mixed with Portland cement Pl 275, which had a Blaine-index of 2490 sq. cm./gram, in the ratio of 1 part phosphorus furnace slag to 2 parts Portland cement. The symbol PZ 275" stands for a Portland cement with a crushing strength of at least 275 'kg./sq. cm. after a hardening period of 28 days.

The following test data were obtained. The test data -for P2 275 are indicated for the purpose of comparison.

The crushing strength was determined in this and the following Examples on prisms with edges 4-4'16 cm. long, in accordance with testing method DIN 1164.

stands for a Portland cement with a crushing strength of at least 375 kg./sq. cm., after a hardening period of 28 days.

5 Mixture PZ 375 (1:1)

P2 275 313) i i%8f.f1 543 389 After 365 days 657 765 Crushlng strength kg./sq. 0111.: Heat of hydration caL/gram:

After 28 da 413 200 After 1 day 79. 5 38. 7 After 365 days 599 317 After 7 days 93. 7 5s. 0 Hesioghgdggtion caL/gram: 59 8 8 After 7 (1&5:IIIIIIIIIIIIIIIIIII: 79. 6 33$; What is claimed is:

1. A cement-based hydraulic binder consisting of a mix- EXAMPLE 2 tugre 05 a slag from electro-theimbzll furnacle5 progu7cggn of p osp orus in a proportion o tween an o y grpund phosphorus furnacejlag of Example 1 was weight and the balance Portland cement, the slag being nmfed wlth Portland cement, P2 275 of Example ground to cement fineness and containing by weight about I, 111 the T211110 Of 121. Th6 following data were obtained: 4 of c o about 2% s o and about 2 of A12O3 2. Massive concrete prepared with the hydraulic binder Mixture of claim 1. P2 275 (111) References Cited ffigg gg g ke/sq- 280 UNITED STATES PATENTS i zggggegg- 1,326,433 10/1931 Pistor et al.

Ami!(1: 85:IIIIIII:IIIIIIIIIIIIIII 79.6 41.1 QTHER REFERENCES Eitel: Silicate Science, vol. 5, pp. 515-516, 1966, Aca- EXAMPLE 3 demic Press, New York.

The phosphorus furnace slag of Example 1 was mixed JAMES PQER, primary Examiner with Portland cement P2 375, which had a Blaineindex of 4140 sq. cm./grarn, in the ratio of 1:1. The following test data were obtained. The symbol P2 375 US. Cl. X.R. 10697, 103, 117 

